Ultra high frequency wide-band tuner



E. O. SELBY ULTRA-HIGH FREQUENCY WIDE-BAND vTUNER Filed Dec. 28, 1943 EUEENEEIAZIEVETREY CQM Patented Sept. 9, 1947 2,427,110 ULTRA HIGH FREQUENCY WIDE-BAND TUNER Eugene 0. Selby, Collingswood, N. J assignor to Radio Corporation of America,

of Delaware a corporation Application December 28, 1943, Serial N0. 515,905

12 Claims. (Cl. 178-44) This invention relatesgenerally to ultra-high frequency apparatus and particularly to a wideband ultra-high frequency tuner employing adjustable capacitive elements.

One of the conventional methods of tuning at ultra-high frequencies is to employ a resonant line of suitable design across one end of which is connected a variable capacitor having a relatively high maximum capacity. Such an arrangement provides a theoretical limit of 1 to 2 between minimum and maximum frequency adjustments. In practice, the theoretical limit is not attainable because of non-uniform circuit constants. In addition, the loading efiect of the device to which the tuner is connected reduces the practicable tuning frequency band.

The instant invention is an improvement upon the invention disclosed in the copending U. S. aplication of Alfred H. Turner, SerialNo. 481,215, filed March 31, 1943, now Patent No. 2,408,895 issued October 8, 1946, entitled Ultra-high frequency tuner, which is assigned to the same assignee as the instant application. The copending application contemplates the use of a resonant line connected at one end to a suitable utilization circuit. The opposite ends of the line are connected together through one or more variable capacitors and an inductive element having an inductance of the order of that of one of the lines. The resulting circuit comprises a parallel resonant circuit including the utilization device .and the resonant lines, having a series-tuned circuit including the capacitive and the inductive elements connected across the ends of the lines remote from the utilization device. Adjustment of the reactance of the series capacitors effectively provides simultaneous adjustment of both the capacitive and inductive reactances of the circuit. Such an arrangement provides a theoretical limit of one tothree between the minimum and maximum tuning frequency limits. Of course, the theoretical limits are not attainable in actual practice, but the practical limits attainable substantially exceed those possible with the conventional tuning arrangement described heretofore.

The instant invention also is an improvement over another copending application of Alfred H. Turner, Serial No. 512,107, filed November 29, 1943, now Patent No. 2,408,896 issued October 8, 1946, entitled "Microwave multiband tiiner. The last-mentioned Turner application describes apparatus which includes means for tuning over a plurality of relatively wide ultra-high frequency bands, and especially means for maintaining substantially constant the pass band of the tuning apparatus over all portions of each of the tuning ranges. Conventional wafer type switches are employed for switching between the various tuning bands. The inductive coupling between the various tuned circuits of a superheterodyne radio frequency amplifier, converter and local oscillator is supplemented by fixed capacitive coupling in the regions of voltage nodes in the tuning circuits, for providing the required additional coupling between said circuits over predetermined portions of each of the tuning bands.

The instant invention provides relatively wideband tuning, or the equivalent of multi-band tuning on a plurality of adjacent frequency bands, by employing tuned circuits which comprise a half-wave resonant circuit or line coupled through a first variable capacitor to a second resonant circuit or line which is slightly less than one-half wavelength. The second resonant circuit or line is coupled through a second variable capacitor to a third resonant circuit or line which is slightly less than one-quarter Wavelength. The remaining terminal of the third resonant circuit or line is grounded, or otherwise terminated.

While the devices described in the two copending applications provide a theoretical maximum tuning frequency range of 3 to 1, the instant invention provides a theoretical maximum tuning frequency range of 5 to 1. This frequency range may be extended by inserting additional resonant circuits or lines of less than one-half wavelength between the second and third resonant circuits or lines mentioned heretofore, and by coupling the additional lines to the adjacent resonant circuits or lines by means of additional variable tuning capacitors. For example, four resonant lines and three series tuning capacitors provide a maximum to minimum frequency ratio of 7 to 1, while five resonant circuits orlines coupled togetherby four tuning capacitors provide a maximum to minimum tuning frequency ratio of 9 to 1. The several tuning capacitors may be adjusted simultaneously or successively, as desired, and may be ganged or successively actuated in any manner known in the art.

A second modification of the instant invention comprises a tubular resonant line having an efiective electrical length of one-half wavelength, which is coupled capacitively to a'solid resonator having an effective length of slightly less than one-half wavelength. The solid resonator,in turn, is coupled capacitively to a'second tubular resonant line having an efiective length of slightly less than one-quarter wavelength. This arrangement provides a theoretical maximum tuning frequency range of 5 to 1, which may be extended by employing additional resonant tubular lines and solid resonators each having slightly -'"different effective lengths of slightly less than one-half wavelength.

A third modification of the instant invention employs paralled resonant lines in the form of. flat straps having lengths of one-half wavelength, slightly less than one-half wavelength, and slightly less than one-quarter Wavelength. The sections of lines are connectedtinseries .by .means of coupling capacitors. The resonant frequency of the system is varied by variation of the coupling capacities which variation is accomplished by moving the intermediate section of line with respect to the end sections.

The reason that the second, third, fourth and fifth 1ines,- :or .resommt -:circuits,1are proportioned to resonate :at :slightly .less than one-half wavelength, or slightly less than one-quarter "wavelength, is to-qnin'rmize "the possibility of similarly tuned resonant circuits or lines resonatingfat approidmately .the .zsame resonant frequency, thereby providing double resonance effects.

The various embodiments "of applicants improved tuningadevice willbe described in greater detail hereinafter particularly with :respect to the application thereof to ultra-high frequency oscillator .and amplifier circuits and apparatus.

Among theobjects of the invention :are to providezan improved methodio'f andmeans for tuning :an ultra-high frequency circuit. Another object of the invention :is to provide an improved method of and means .for'varyin'g simultaneously the effective inductive'and capacitive reactance in anZultra-highfrequency "circuit. .A further objectof -the-invention is to provide an improved method of "and means ifor tuning an "ultra-high frequency icircuit over aifr'equency band having a'maximum toaninimumire ueHcy ratio of more than .3 .to 11.

Additional objects of theinvention include an improved :method 'of and means -.for providing adjustable rcapacitive :coupling between a "plurality Inf different :resonant circuits or lines .to vary 'theresonantfre'quency of the network 'over a frequency band havinga maximum frequency corresponding to theorder of half wave resonance of oneof said linesiand a-minimum frequency correspondingto'the order of the combined quarter wave" resonancepf all nof said'coupled lines or circuits connected in series. Another object of the invention is to provide -an=improved ultrahigh frequency wide-band tuner employing a plurality of differentlyresonant sections of tubular iline :and'solid resonators which are adjustably capacitively coupled together. A- further object' Of theTinVentiOn is to provide an improved method of and means for employing a plurality of parallel resonant linesihaving different resonantlcharac'teristics, :said lines being .adjustably coupled together to providean adjustable series resonant circuit.

Other objects of the invention include the provision of novel means .for capacitively serially connecting a plurality -of resonant. circuits or lines,and means* for simultaneously adjusting each of saidiseries-connected capacitive elements. Anotherebject of the invention is to provide an improved methodof and meansfor serially connecting a plurality of I resonant circuits or :lines by means of a plurality of adjustable capacitive elements, and means for successively adjusting each of said capacitive elements.

The invention will be described in greater detall by reference to the accompanying drawing of which Figure 1 is a schematic circuit diagram of a'first embodiment of itheinventionincluding an ultra-high-frequency oscillatorcircuit including a tuned circuit having a theoretical maximum to minimum tuning frequency ratio of 3 to 1; Figure 2 is a schematic circuit diagram of a modification of 'said first embodiment including an "ultra-high frequency circuit having a theoretical'maximumito minimum tuning frequency ratio ef T5 to 1'; 'Figureb3 is a cross-sectional schematic diagram-of a second embodiment of the invention, and Figure 4: is a cross-sectional schematic diagram of a third embodiment of the invention. Similar reference characters are applied to similar elements throughoutthe drawing.

Referring to Figure .1, an ultra-high frequency thermionic tube oscillator circuit, employing a resonant circuit in accordance with the invention, includes a lighthouse type ultra-high frequency tube 1, having its anode electrode 2 connectedto one end of aresonant conductor 3 having an effective length of /2 wavelength at the maximum operating frequency, and having its cathode electrode connected .to one end of a second half-wave resonant'conductor 5. The remaining terminalof .thefirst half-wave conductor 3 .is-connected, through afirst adjustable capacitor .1, to one end of a third resonant conductor Shaving a length of slightly. less than one-quarter wavelength at the maximum operating frequency. The-remaining terminal of the second half wave conductor 15 is connected, through a second-adjustable capacitor .l l, to -.one terminal of a fourth resonant'line .l-3having similar dimensions to the third resonant line 9. The remaining terminals of thethirdand fourth resonant lines 9, 13, respectively, areconnectedtogetherand grounded.

The control electrode M of the thermionic tube l is connectedtoground through first and second feedback capacitors l5 and H. A third feedback capacitor 19 is connected between the first and second resonant 1ines3, 5 adjacent the anode .and cathode electrodes 2,4, respectively. The feedback capacitors I5, I! and I9 thereby provide sufficient regeneration to provide sustained oscillations at the'resonant frequency of the circuits as determined 'by the adjustable capacitances .of the tuningcapacitors I, ll, respectively. Preferably, the tuning capacitors 1, ll areganged together, as indicated by the dash line 2 I.

.The theoretical maximum-to-minimum tuning frequency limits of the oscillator circuit thus described have a ratio of 3 to 1 if the first and second tuninggcapacitors 1, [I have a minimum to-maximum capacity range of zero to infinity. Since the tuning capacitors have finite limits, the practical tuning range .is slightly less than 3 to '1. Connection for operating voltages to the thermionic tube I have been omitted. to simplify the description of the circuit. Such connections may'be made in any mannerknown inthe art.

iFigure'2 shows .a modification .of the circuit ofiFigure 1 adapted to ,provide a maXimum-tominimum tuningfrequency ratio of slightly less than 5 to 1, .under practical operating conditions. The feedback capacitors have been omitted (for the sake of simplicity. .The anode 2 of thethermionic tube -l :is'connected to one end of a first resonant line 3 having an effective length of wavelength at the highest operating frequency. The cathode electrode 4 of the thermionic tube I is connected to one end of a second half-wave line or resonant circuit 5. The remaining terminal of the first half-wave line 3 is connected, through a first tuning capacitor 7, to one end of a third resonant line 8 having an effective length of slightly less than /2 wavelength at the highest operating frequency. The remaining terminal of the third resonant line 8 is connected, through a second tuning capacitor ll], to one end of a fourth resonant line 9 having an effective length of slightly less than wavelength at the highest operating frequency.

Similarly, the remaining terminal of the second resonant circuit 5 is connected, through a third tuning capacitor l l, to 'one end of a fifth resonant line I2 having an effective length of slightly less than 1 wavelength at the highest operating frequency. The remaining end of the fifth resonant line I2 is connected, through a fourth adjustable tuning capacitor E5, to one end of a sixth resonant line l3 having an effective length of slightly less than wavelength at the highest operating frequency. The remaining terminals of the fourth and sixth quarter-wave lines 9, l3, are connected together and grounded. The control electrode M of the thermionic tube l is grounded directly for amplifier circuits, or through a capacitor (not shown) for oscillator circuits. The adjustable tuning capacitors F, iii, ll and it maybe ganged together as indicated by the dash line 22 or may be successively actuated in any desired manner. Although not indicated in the drawing, the feedback capacitors i5, 11, I9 may be connected in the same manner as shown in Figure 1 to provide sustained osci1 laticns.

The device of Figure 3 provides a 5 to 1 maximum-to-minimum tuning frequency ratio by means of half-Wave and quarter-wave tubular line resonators which are capacitively coupled together by means of half-wave solid resonators. The anode 2 of the thermionic tube l is in serted, through an aperture 3i, in a first tubular line resonator 32 having'an effective electrical length of wavelength at the highest operating frequency. Similarly, the cathode 4 of the thermionic tube I is connected to a second tubular line resonator 33 having an effective length of wavelength at the highest operating frequency. The ends of the first and second tubular line resonators 32, 33 remote from the corresponding thermionic tube electrodes 2, 4, respectively, are apertured, and include insulating sleeve 40, to receive first and second solid resonators 34, 35, each of which has an effective electrical length of slightly less than wavelength at the highest operating frequency. The remaining ends of the solid resonators 34, 35 are coupled, respectively, to third and fourth tubular line resonators 33, 31, which have effective electrical lengths of slightly less than wavelength at the highest operating frequency. The re maining ends of the third and fourth tubular line resonators 36, 31, respectively, remote from the solid resonators 34, 35, are closed by means of conductive plugs 3B, 39 respectively, and grounded.

Tuning of the circuit is accomplished by changing the relative longitudinal positions of the solid resonators 34, 35, to vary the relative penetration thereof within the tubular line resonators associated therewith, resulting in variation of I the capacitive coupling between the sections of line. Both the solid resonators 34, 35, and the quarter-wave tubular line resonators 36, 3'! may be made longitudinally adjustable with respect to the half wave cavity resonators 32, 33, if desired. Likewise, the longitudinal adjustment of the solid resonators 34, and the quarterwave cavity resonators 36, 3?, may be ganged to provide simultaneous or successive positional adjustment thereof. The control electrode M of the thermionic tube l is directly grounded for amplifier circuits or may be grounded through a capacitor for oscillator circuits in the same manner as described heretofore in Figure 2.

Figure 4 is similar to Figure 3 with the exception that parallel flat strap resonant lines are substituted for the tubular line resonators of the device of Figure 3. First and second fiat strap resonant lines 42, 43, each having an efiective length of wavelength at the highest operating frequency, are connected, respectively, to the anode and cathode electrodes, of the thermionic tube l. Third and fourth open-circuited resonant lines 44, 4-5, each having an effective length of slightly less than /2 wavelength at the highest operating frequency, are disposed in adjustable capacitive relation to the open-circuited ends of the first and second resonant lines 42, 43, respectively. In a like manner, the open-circuited ends of fifth and sixth resonant lines 46, 47, each having an effective length of slightly less than wavelength at the highest operating frequency, are disposed in adjustable capacitive relation to the remaining open-circuited ends of the third and fourth resonant lines 44, 45. The remaining ends of the fifth and sixth quarter-wave resonant lines are connected together and grounded. The control electrode I4 is shown directly grounded for simplicity. Such connection is applicable for amplifier circuits. For oscillator circuits, feedback capacitors as shown in Figure 1 are employed.

Tuning of the circuit is provided by longitudinal or vertical adjustment of the positions of the open-circuited third and fourth resonant lines 44, 45, with respect to the remaining resonant lines; as indicated by the arrows 48. If desired, the third and fourth open-circuited half wave resonant conductors 44, 45 may be rotated in a plane normal to the axes of the remaining resonant lines, in order to vary both the inductive and-the capacitive coupling between the several resonant lines. Similarly, the positional adjustment of the movable resonant lines may be provided simultaneously or successively, as indicated by the dash lines '49.

Thus the several embodiments of the invention described comprise means for simultaneously or successively tuning a plurality of half-wave and quarter-Wave resonant lines, circuits, cavity resonators or solid resonators, whereby adjustment of the mutual coupling between adjacent circuit elements provides means for obtaining ultra-high frequency tuning over extended frequency bands. 7 It should be understood that the frequency response curve of'the various modifications of the invention disclosedherein may be varied by conventional mechanical linkages or coupling devices inany manner known in the art. a i

The circuit configurations described herein are adaptable for :interstage coupling where these circuits are employed, for instance, in a radio receiver wherein" interstage coupling may herequired; between an oscillator stage, mixer stage and R. F. amplifier stages. For such applications, the resonant lines of adjacent stages may be located parallel to each other, so that magnetic or capacitive coupling, or combinations of these couplings, may be employed as desired and controlled by interstage shielding.

The above described tuning means provides a system for wide band coverage without the use of variable conductive contacts between elements of the circuit, thus eliminating one of the common sources of noise resulting from imperfect contacts.

I claim as my invention:

1. An ultra-high-frequency tuner including a plurality of serially coupled quarter-wave and half-wave resonant transmission line sections, separate adjustable capacitive means coupling adjacent ends of each of said lines, and means for adjusting said capacitive means to vary the resonant frequency of said tuner over a frequency band having a frequency ratio greater than 3 to 1 with a maximum frequency corresponding to the order of half-wave resonance of one of said lines and a minimum frequency corresponding to the order of the combined quarter-wave resonance of all of said coupled lines.

2. An ultra-high-frequency tuner including a plurality of serially coupled quarter-wave and half wave resonant transmission line sections, separate adjustable capacitive means coupling adjacent ends of each of said lines, and means for simultaneously adjusting said capacitive means to vary the resonant frequency of said tuner over a frequency band having a frequency ratio greater than 3 to 1 with a maximum frequency corresponding to the order of halfwave resonance of one of said lines and a minimum frequency corresponding to the order of the combined quarter-wave resonance of all of said coupled lines.

3. An ultra-high frequency tuner including a plurality of serially coupled quarter-wave and half wave resonant transmission line sections, separate adjustable capacitive means coupling adjacent ends of each of said lines, and means for successively adjusting said capacitive means to vary the resonant frequency of said tuner over a frequency band having a frequency ratio great er than 3 to 1 with a maximum frequency corresponding to the order of half-wave resonance of one of said lines and a minimum frequency corresponding to the order of the combined quarter-wave resonance of all of said coupled lines.

4. An ultra-high frequency tuner including a plurality of serially coupled quarter-wave and half-wave resonant circuits, separate adjustable capacitive means coupling adjacent ends of each of said circuits, and means for adjusting said capacitive means to vary the resonant frequency of said tuner over a frequency band having a frequency ratio greater than 3 to 1 with a maximum frequency corresponding to the order of half-wave resonance of one of said circuits and a minimum frequency corresponding to the order of the combined quarter-wave resonance of all of said coupled circuits.

5. An ultra-hi-gh-frequency tuner including a plurality of serially coupled quarter-wave and half-Wave resonant circuits, separate adjustable capacitive means coupling adjacent ends of each of said circuits, and means for adjusting said capacitive means to vary'the resonant frequency of said tuner over a frequency band having a frequency ratio greater than 3 to I with a maximum frequency corresponding to the order of halfwave resonance of one of said circuits and a minimum frequency corresponding to the order of the combined half-wave resonance of all of said coupled circuits.

6. An ultra-high-frequency tuner including a first resonant line having a length of the order of one-half wavelength at the highest operating frequency, a second line having a length substantially les than one-half wavelength at said highest operating frequency, first adjustable capacitive means coupling one end of said first line to the adjacent end of said second line, a third line having a length substantially less than onequarter wavelength at said highest operating frequency, second adjustable capacitive means coupling the remaining end of said second line to the adjacent end of said third line, and means for adjusting at least one of said capacitive means.

7. An ultra-high-frequency tuner including a first resonant line having a length of the order of one-half wavelength at the highest operating frequency, a second line having a length substantially less than one-half wavelength at said highest operating frequency, first adjustable capacitive means coupling one end of said first line to the adjacent end of said second line, a third line having a length substantially less than one-quarter wavelength at said highest operating frequency, second adjustable capacitive means coupling the remaining end of said second line to the adjacent end of said third line, and means for simultaneously adjusting said capacitive means to provide a maximum to minimum tuning frequency ratio of substantially greater than 3 to 1.

8. An ultra-high-frequency tuner including a first resonant line having a length of the order of one-half wavelength at the highest operating frequency, a second line having a length substantially less than one-half wavelength at said highest operating frequency, first adjustable capacitive means coupling one end of said first line to the adjacent end of said second line, a third line having a length substantially less than one-quarter wavelength at said highest operating frequency, second adjustable capacitive means coupling the remaining end of said second line to the adjacent end of said third line, and means for successively adjusting said capacitive means to provide a maximum to minimum tuning frequency ratio of substantially greater than 3 to 1.

9. An ultra-high-frequency tuner including a first tubular line resonator having an electrical length of the order of one-half wavelength at the highest operating frequency, a utilization device coupled to said first resonator, a second resonator structure having an electrical length substantially less than one-half wavelength at said highest operating frequency, first adjustable means coupling said first tubular line resonator to the adjacent end of said second resonator structure, a third tubular line resonator having an electrical length substantially less than one-quarter wavelength at said highest operating frequency, second adjustable means coupling the remaining end of said second resonator structure to said third tubular line resonator, and means for simultaneously' adjusting said coupling means to provide a maximum to minimum tuning frequency ratio of substantially greater than 3 to 1.

10. An ultra-high-frequency tuner including a first tubular line resonator having an electrical length of the order of one-half wavelength at the highest operating frequency, a utilization device coupled to said first resonator, a second resonator structure having an electrical length substantially less than one-half wavelength at said highest operating frequency, first adjustable means coupling said first tubular line resonator to the adjacent end of said second resonator structure, a third tubular line resonator having an electrical length substantially less than onefrequency, a utilization device terminating one end of said first line, a second line having a length substantially less than one-half wavelength at said highest operating frequency, first means for adjusting the capacitive coupling between the remaining end of said first line and the adjacent end of said second line, a third line having a length substantially less than onequarter wavelength at said highest operating frequency, second means for adjusting the capacitive coupling between the remaining end of said second line and the adjacent end of said third line, means for terminating the remaining end of said third line in said utilization device, and 35 first resonant line means for simultaneously adjusting said capacitive coupling means to provide a maximum to minimum tuning frequency ratio of substantially greater than 3 to 1.

12. An ultra-high-frequency tuner including a having a length of the order of one-half wavelength at the highest operating frequency, a utilization device terminatmg one end of said first line, a second line having a length substantially less than one-half wavelength at said highest operating frequency, first means for adjusting the capacitive coupling between the remaining end of said first line and the adjacent end of said second line, a third line having a length substantially less than onequarter wavelength at said highest operating frequency, second means for adjusting the capacitive coupling between the remaining end of said second line and the adjacent end of said third line, means for terminating the remaining end of said third line in said utilization device, and means for successively adjusting said capacitive coupling means to provide a maximum to minimum tuning frequency ratio of substantially greater than 3 to 1.

EUGENE 0. SELBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,232,591 Davies Feb. 18, 1941 

